Method of preparing carbon nanomaterials

ABSTRACT

This disclosure relates generally to the field of carbon, graphene, energy storage materials, carbon films, and nanocomposites. Specifically, this disclosure relates to novel eco-friendly, cost-effective methods of preparing doped and/or intercalated carbon nanomaterials.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalPatent Application No. 62/968,958, filed Jan. 31, 2020, which isincorporated by reference in its entirety.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

This disclosure relates generally to the field of carbon, graphene,energy storage materials, carbon films, and nanocomposites.Specifically, this disclosure relates to novel eco-friendly,cost-effective methods of preparing doped and/or intercalated carbonnanomaterials.

Description of Related Art

Carbon has several forms including amorphous carbon, carbon nanotubes,graphene, graphite, diamond, and the different carbon atom arrangementsresults in unique properties. The building block for several forms ofcarbon, graphene has been demonstrated to exhibit an extremely largespecific surface area (e.g., 2630 m²/g), good thermal conductivity(e.g., ca.5000/mK for single-layer graphene), high Young's modulus(e.g., 1.0 TPa), high charge mobility (e.g., 200 000 cm²/Vs), excellentoptical transparency, and flexibility. These superior properties makegraphene a promising candidate for a large variety of applications,including energy storage.

The pristine graphene without foreign atom, however, is a zero bandgapmaterial. As a result, this severely limited its application inelectronic and many other devices. Adding foreign atom(s) or doping thecarbon atoms in the graphitic structure or intercalation of the carbonstructure is essential. The introduction of foreign atoms into carbonnetworks could cause electron modulation to change the chargedistribution and electronic properties of carbon skeletons, which inturn affects their work function for electronic applications andenhances interactions with reactants to impart catalytic activities.Doping of the edge of graphene sheets with foreign atoms without damageof the carbon basal plane can also change its work function and impartsolubility and catalytic activity while largely retaining thephysicochemical properties of the pristine graphene. The dangling bondsat the edge of a graphene sheet have been demonstrated to be morereactive than the covalently bonded carbon atoms within the basal plane.As a result, edge-doping/functionalizing graphene materials can be takenas a promising approach to tune their properties for specificapplications. Also, intercalation of the network carbon with foreignatoms provides a fully intercalated state material for electrochemicaldevices.

SUMMARY OF THE DISCLOSURE

One aspect of the disclosure provides a process for preparing a carbonnanomaterial. The carbon nanomaterial of the disclosure is doped and/orintercalated. Such process includes:

-   -   providing a carbon-containing material to a reactor comprising a        solvent;    -   providing one or more of: an oxidizing or reducing solution, and        a doping and/or intercalating agent to the reactor comprising        the carbon-containing material to obtain a reaction mixture,    -   heating the reaction mixture to a temperature and for a time        period sufficient to obtain an intermediate material; and    -   further heating the intermediate material to a temperature and        for a time period sufficient to obtain the carbon nanomaterial.

Another aspect of the disclosure provides a carbon nanomaterial preparedby the process of the disclosure as described herein.

Another aspect of the disclosure provides methods for preparing a filmof the carbon nanomaterial of the disclosure as described herein. Suchmethods include

-   -   providing a carbon-containing material to a reactor comprising a        solvent;    -   providing one or more of: an oxidizing or reducing solution, and        a doping and/or intercalating agent to the reactor comprising        the carbon-containing material to obtain a reaction mixture;    -   heating the reaction mixture to a temperature and for a time        period sufficient to obtain an intermediate material;    -   further heating the intermediate material to a temperature and        for a time period sufficient to obtain the carbon nanomaterial;    -   providing the carbon nanomaterial and one or more of additives        selected from a conductive agent, binder, and thickening agent,        to a second solvent to obtain the slurry of the carbon        nanomaterial;    -   coating a surface of a substrate with the slurry to obtain a        coated substrate; and heating the coated substrate to a        temperature and for a time period sufficient to obtain the        carbon nanomaterial film.

Another aspect of the disclosure provides methods for preparing ananocomposite comprising the carbon nanomaterial of the disclosure asdescribed herein. Such methods include

-   -   providing a carbon-containing material to a reactor comprising a        solvent;    -   providing one or more of: an oxidizing or reducing solution, and        a doping and/or intercalating agent to the reactor comprising        the carbon-containing material to obtain a reaction mixture;    -   heating the reaction mixture to a temperature and for a time        period sufficient to obtain an intermediate material;    -   further heating the intermediate material to a temperature and        for a time period sufficient to obtain the carbon nanomaterial;    -   providing the carbon nanomaterial to a polymer to obtain the        nanocomposite.

Another aspect of the disclosure provides an electrochemical cell. Suchcell includes a cathode comprising the carbon nanomaterial film of thedisclosure as described herein, an anode, an electrolyte in fluidcommunication with the cathode and the anode, and a separator disposedbetween the anode and the cathode.

These and other features and advantages of the claimed invention will bemore fully understood from the following detailed description takentogether with the accompanying claims. It is noted that the scope of theclaims is defined by the recitations therein and not by the specificdiscussion of features and advantages set forth in the presentdescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the compositions and methods of the disclosure and areincorporated in and constitute a part of this specification. Thedrawings illustrate one or more embodiment(s) of the disclosure and,together with the description, serve to explain the principles andoperation of the disclosure.

FIG. 1 and FIG. 2 show a transmission electron micrograph of thedoped-graphene prepared from corn at 750° C. as disclosed in Example 1.

FIG. 3 shows scanning electron micrographs (10,000× magnification) ofdoped-graphene sheets prepared as disclosed in Example 1.

FIG. 4 shows scanning electron micrograph of doped-graphene prepared asdisclosed in Example 1, with two testing spots

FIG. 5 and FIG. 6 show a scanning electron micrograph showingdoped-graphene prepared from rice grain at 1000° C. as disclosed inExample 2.

FIG. 7 shows a scanning electron micrograph of the doped-grapheneprepared from cassava at 1000° C. as disclosed in Example 3.

FIG. 8 shows a scanning electron micrograph of the doped-grapheneprepared from rice grain at 850° C. as disclosed in Example 4.

FIGS. 9-11 show scanning electron micrographs of wrapped-nanosheetsformed from pyrolysis of cassava extract (FIG. 9 , 100,002×magnification), rice grain (FIG. 10 , 80,000× magnification) and corn(FIG. 11 , 65,000× magnification) as disclosed in Example 5.

FIGS. 12-14 show scanning electron micrographs of wrapped-graphenesheets grown from corn husk at different temperatures as disclosed inExample 6. FIG. 12 shows the process at 800° C. (100,000×magnification); FIG. 13 shows the process at 900° C. (35,000×magnification); FIG. 14 shows the process at 1000° C. (50,000×magnification);

FIG. 15 shows a transmission electron micrograph of the wrapped-grapheneprepared from corn husk at 1000° C. as disclosed in Example 6.

FIG. 16 shows scanning electron micrographs of wrapped-graphene preparedas disclosed in Example 7.

FIG. 17 shows the rate test of coin cells showing the performance ofsample A and B as active anode material at different rates.

FIGS. 18A-18C show the rate test data of coin cell of sample B atdifferent rates. FIG. 18A shows the test data at 0.1 C; FIG. 18B showsthe test data at 0.1 C, 0.2 C, and 0.5 C; FIG. 18C shows the test dataat 1 C, 5 C, and 10 C.

FIG. 19 shows the delithiation rate mapping of the coin cell ratecapability, as an average of up to 9 cells. Discharge C-Rate of “0”shows 0.1 C. Top panel shows the mapping of baseline anode, and thebottom panel shows the mapping of the electrode prepared from the carbonnanomaterial as disclosed in Example 8-4.

FIG. 20 shows the initial cycling of the coin cell cycle life, as anaverage of up to 9 cells. Top panel shows the cycling of baseline anode,and the bottom panel shows the cycling of the electrode prepared fromthe carbon nanomaterial as disclosed in Example 8-4.

DETAILED DESCRIPTION OF THE DISCLOSURE

Before the disclosed processes and materials are described, it is to beunderstood that the aspects described herein are not limited to specificembodiments, and as such can, of course, vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular aspects only and, unless specifically definedherein, is not intended to be limiting.

In view of the present disclosure, the compositions and methods providea doped and/or intercalated carbon nanomaterial that can be used forfabrication of advanced materials, including but not limited to,ultra-high energy storage devices, ultra-sensitive catalyst, highcapacity and activity filters, composites and impact resistance devices.The methods of the disclosure can also be used to produce doped and/orintercalated carbon nanomaterial on various substrates or to producenanocomposites comprising the doped and/or intercalated carbonnanomaterial.

As provided above, one aspect of the disclosure provides a process forpreparing a doped and/or intercalated carbon nanomaterial of thedisclosure. For example, the carbon nanomaterial may be Li-, Na-, O-,P-, K-, and/or Si-doped. In certain embodiments, the carbon material ofthe disclosure comprises up to 2 wt % of doping. In another example, thecarbon nanomaterial may be in a form of a particulate, porous foam,film, or pellet, or is dispersed in a solvent.

In the process, a carbon-containing material is provided to a reactorcomprising a solvent. In certain embodiments, the suitablecarbon-containing material includes a carbon nanosheet, graphene,fullerene, amorphous carbon, graphene oxide, carbon black, activatedcarbon, charcoal, carbon nanotubes, graphite, coal, and a combinationthereof. In certain embodiments, the suitable carbon-containing materialincludes is or is derived from the group consisting of cassava root,tapioca flour, yam root, potato root, sugarcane, sugar beet, sucrose,rice grain, corn, and wheat grain. For example, the carbon-containingmaterial comprises cassava root extract, cassava root flour, tapiocaflour, dried cassava root pulp, dried and fried cassava root flakes, yamroot extract, or potato root extract. In certain embodiments, thecarbon-containing material comprises sugarcane extract, sugar beet rootextract, or sucrose. In certain embodiments, the carbon-containingmaterial comprises rice grain or corn or wheat grain.

The solvent suitable for the process of the disclosure as describedherein includes, but is not limited to, distilled water, deionizedwater, ethanol, N-methyl-2-pyrrolidone (NMP), ethylene glycol, propyleneglycol, or a combination thereof. The solvent may soak or dissolve(fully or partially) the carbon-containing material.

To the reactor comprising the carbon-containing material and thesolvent, to obtain a reaction mixture, one or more of: an oxidizing orreducing solution, and a doping and/or intercalating agent is provided.In certain embodiments, the oxidizing or reducing solution is selectedfrom one or more of: sodium hydroxide, potassium hydroxide, hydrochloricacid, phosphoric acid, phosphorous acid, and nitric acid. In certainembodiments, the oxidizing or reducing solution is phosphoric acid(e.g., 75%) or sodium hydroxide (e.g., 5%).

The doping and/or intercalating agent suitable for use in the methods ofthe disclosure includes organic or inorganic salts of lithium, sodium,potassium, magnesium, calcium, aluminum, and silicon. For example, incertain embodiments, the doping and/or intercalating agent of thedisclosure is selected from lithium chloride, 3,4-dihydroxybenzonitriledilithium, lithium hydroxide, lithium acetate, lithium citrate, lithiumbis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate,aluminium triacetate, calcium hydroxide, magnesium acetate, siliconoxide, and a combination thereof. In certain embodiments, the dopingand/or intercalating agent is lithium acetate, lithium hydroxide, orsilicon oxide. In certain embodiments, the doping and/or intercalatingagent is lithium acetate or lithium hydroxide,

As provided above, in the process of the disclosure, the reactionmixture (e.g., comprising the carbon-containing material and one or moreof: an oxidizing or reducing solution and a doping and/or intercalatingagent in the solvent) is heated to a temperature and for a time periodsufficient to obtain an intermediate material. Heating in the process ofthe disclosure may be accomplished by any suitable means known to thoseof skill in the art, such as by using resistive element source, laserirradiation, microwave irradiation, etc.

In certain embodiments, the reactor is charged with partial oxygen orinert gas (such as argon, helium, or nitrogen) prior to heating. Incertain embodiments, the reactor is charged with a partial pressure ofhydrogen gas in an inert gas (such as argon, helium, or nitrogen).

The temperature sufficient to obtain the intermediate material, incertain embodiments, is in a range of about 45 to 1050° C. For example,the reaction mixture may be heated to a temperature in a range of about50 to 200° C., 60 to 200° C., 70 to 200° C., 100 to 200° C., 50 to 150°C., 60 to 150° C., 70 to 150° C., 100 to 150° C., 50 to 120° C., 60 to120° C., 70 to 120° C., or 100 to 120° C. The time sufficient to obtainthe intermediate material, in certain embodiments, is in a range ofabout 1 hour to 36 hours. For example, the reaction mixture may beheated for a time in a range of about 6 to 36 hours, 6 to 24 hours, 6 to18 hours, 6 to 12 hours, 12 to 36 hours, 12 to 24 hours, 12 to 18 hours,18 to 30 hours, 20 to 28 hours, 22 to 26 hours, or 24 to 36 hours. Incertain embodiments, the reaction is heated for about 24 hours.

After forming the intermediate material, in certain embodiments, thereducing or oxidizing solution and/or the doping and/or intercalatingagent may be removed from the mixture by any suitable means known tothose of skill in the art. For example, the reducing or oxidizingsolution may be removed by filtering, or by washing and diluting withexcess distilled or deionized water. The doping and/or intercalatingagent may be removed by washing, filtering, magnetic separation,sonication, sieving, and centrifugation.

The intermediate material may also be dried prior to further heating inorder to obtain the carbon nanomaterial.

In certain embodiments, the intermediate material may be contacted withone or more of the doping and/or intercalating agents prior to furtherheating. In some embodiments, the doping and/or intercalating agent isnot provided to the reactor to form the reaction mixture (e.g., thereaction mixture comprising the carbon-containing material and one ormore of an oxidizing or reducing solution in the solvent), and theintermediate material may be contacted with one or more of the dopingand/or intercalating agents prior to further heating.

In certain embodiments, the intermediate material may be contacted withone or more of hydrazine (N₂H₄), lithium aluminium hydride (LiAlH₄),diborane (B₂H₆), and sodium borohydride (NaBH₄) prior to furtherheating. In such process, a network of doped and/or intercalated carbonmaterial in form of a nanosheet or foam is produced.

In the process of the disclosure as described herein, the intermediatematerial is further heated to a temperature and for a time periodsufficient to obtain the carbon nanomaterial. For example, theintermediate material may be heated to a temperature in a range of about500 to 1500° C., such as 600 to 1500° C., 700 to 1500° C., 800 to 1500°C., 900 to 1500° C., 500 to 1000° C., 600 to 1000° C., 700 to 1000° C.,800 to 1000° C., 900 to 1000° C., or 1000 to 1500° C. The timesufficient to obtain the intermediate material, in certain embodiments,is in a range of about 10 minutes to 3 hours. For example, the reactionmixture may be heated for a time in a range of about 0.5 to 3 hours, 0.5to 2 hours, 0.5 to 1.5 hours, 0.5 to 1 hour, 0.75 to 1.25 hours, 1 to 3hours, 1 to 2 hours, or 2 to 3 hours, or about 1 hour.

In certain embodiments, the carbon nanomaterial may be further processedin order to obtain carbon nanomaterial having high surface area, such asa BET surface area of at least 1900 m²/g and pore volume of at least 2.4cm³/g. Thus, in certain embodiments, the process of the disclosurefurther comprises:

-   washing the carbon nanomaterial with hydrogen peroxide or    hydrochloric acid to obtain a washed carbon nanomaterial;-   rising the washed carbon nanomaterial with distilled or deionized    water to obtain a rinsed carbon nanomaterial; and-   heating the rinsed carbon nanomaterial in an third gas at a    temperature in a range of about 700 to 1500° C.

The third gas, in certain embodiments, comprises partial oxygen or aninert gas (e.g., argon, helium or nitrogen). In certain embodiments, theinter gas further comprises a partial pressure of hydrogen gas.

In certain embodiments, the carbon nanomaterial has a BET surface areaof at least 1900 m²/g, such as for example, at least 2000 m²/g, 2100m²/g, 2200 m²/g, 2300 m²/g, and even 2400 m²/g. In certain embodiments,the carbon nanomaterial has a BET surface area of up to 2700 m²/g. Incertain embodiments, the carbon nanomaterial has a pore volume of atleast 2.4 cm³/g, such as for example, at least 2.5 cm³/g, 2.8 cm³/g, 3cm³/g, 3.2 cm³/g, 3.4 cm³/g, 3.6 cm³/g, 3.9 cm³/g, 4 cm³/g, 4.5 cm³/g,or even 4 cm³/g. In certain embodiments, the carbon nanomaterial has apore volume of up to 6 cm³/g, e.g., up to 5.5 cm³/g or up to 5 cm³/g.

The carbon nanomaterial of the disclosure as described herein may bealso mixed with one or more additives in a second solvent in order toobtain a slurry. The second solvent and the one or more additives, suchas conductive agents, binders, and thickening agents, may be selected byone of skill in the art depending on the desired application.

Furthermore, in certain embodiments, the carbon nanomaterial of thedisclosure as described herein may be used to provide a carbonnanomaterial film. The carbon nanomaterial film of the disclosureconfigured for use in an electrochemical cell. Thus one aspect of thedisclosure provides a process for preparing the carbon nanomaterialfilm, the process including:

-   -   providing the carbon nanomaterial prepared by the process of the        disclosure as described herein and one or more of additives        selected from a conductive agent, binder, and thickening agent,        to a second solvent to obtain the slurry of the carbon        nanomaterial;    -   coating a surface of a substrate with the slurry to obtain a        coated substrate; and    -   heating the coated substrate to a temperature and for a time        period sufficient to obtain the carbon nanomaterial film.

Suitable substrates may be coated by tape casting, dip coating, spraycoating, spin coating, electronic printing, lamination, stamping, blockprinting, roller printing, screen printing, and heat transfer printing.

For example, in certain embodiments, the coated substrate may be heatedto a temperature in a range of about 25 to 150° C.

The heating, in certain embodiments, may be under partial oxygen or aninert gas (e.g., argon, helium or nitrogen) atmosphere. In certainembodiments, the inter gas further comprises a partial pressure ofhydrogen gas.

One of skill in the art will recognize that a substrate surface may beprepared for the coating step. For example, in certain embodiments, thesubstrate surface is cleaned with organic solvent and/or acid or base,rinsed with distilled or deionized water, and dried prior to coating.

Another aspect of the disclosure provides a nanocomposite comprising acarbon nanomaterial of the disclosure and a polymer. The disclosure alsoprovides a process for preparing the nanocomposite, comprising providingthe carbon nanomaterial of the disclosure to a polymer.

Suitable polymers include, but are not limited to, high densitypolyethylene and polypropylene, rubber, nylon, epoxy, teflon, andadhesives.

In certain embodiments, the carbon nanomaterial is provided in an amountsufficient to increase one or more of mechanical, absorption,adsorption, electrical, electronic, magnetic, and optical properties ofthe nanocomposite by at least a factor greater than 1 compared to thesame properties of the polymer. For example, the carbon nanomaterial isprovided in an amount in a range of 0.001 to 40 weight %, based on thecombined weight of the carbon nanomaterial and the polymer. In certainembodiments, the carbon nanomaterial is provided in an amount in a rangeof 0.01 to 5 weight % (e.g., 0.01 to 4 weight %, 0.01 to 2 weight %,0.01 to 1 weight %, 0.1 to 5 weight %, 0.1 to 4 weight %, 0.1 to 2weight %, 0.1 to 1 weight %, 1 to 5 weight %, 1 to 4 weight %, 1 to 2weight %, 0.5 to 1 weight %, 2 to 5 weight %, 2 to 4 weight %, 3 to 5weight %, or 4 to 5 weight %), based on the combined weight of thecarbon nanomaterial and the polymer.

Another aspect of the disclosure provides an electrochemical cellcomprising: a cathode comprising carbon nanomaterial film of thedisclosure, an anode, an electrolyte in fluid communication with thecathode and the anode, and a separator disposed between the anode andthe cathode. In certain embodiments, the anode is high energy and highpower density anode. In certain embodiments, the electrolyte consist ofa combination of organic or inorganic solvents containing lithiumcompounds, sodium compounds, potassium compounds, or calcium compounds,such as 3,4-dihydroxybenzonitrile dilithium, lithium hydroxide, lithiumacetate, lithium citrate, lithium bis(trifluoromethylsulfonyl)imide(LiTFSI), or lithium hexafluorophosphate (LiPF₆).

In certain embodiments, the electrochemical cell of the disclosure isconfigured as a coin cell, a pouch cell, a cylindrical cell form-factor,or a pack comprising two or more of the coin cells, pouch cells, orcylindrical cell form-factors.

EXAMPLES

The compositions and methods of the disclosure are illustrated furtherby the following examples, which is not to be construed as limiting thedisclosure in scope or spirit to the specific procedures and compoundsdescribed therein.

Example 1: Preparation of Doped Carbon Nanosheet from Corn

A total of 20.0 g of corn grain was placed in a 500 mL Pyrex glassbeaker. About 5 g of lithium acetate was dissolved in 100 mL solutionand was added to the corn grains in beaker, and the resulting mixturewas stirred thoroughly. 80.0 g of phosphoric acid was added to themixture and exposed to 160° C. for 36 hours in a convection oven in airatmosphere. After heating, the sample formed an intermediate product,which was exposed to further heating on 750° C. in 10% vol. H₂ in He gasflowing at a total rate of 100 mL/min. The sample was ramped at 10°C./min from 20° C. to 750° C. and held at 750° C. for 1 hour. Theresulting product was washed thoroughly in de-ionized water to removeany unreacted precursors, followed by drying in an oven at 80° C.overnight. Transmission electron micrographs showed in FIGS. 1 and 2confirmed the final product is made-up of predominantly carbonnanosheets. Scanning electron micrographs of resulting doped-nanosheetare presented in FIGS. 3 and 4 . The elemental compositions of thedoped-carbon nanosheets performed using energy dispersive spectroscopy(EDS) technique is provided in Table 1 where the sampling was performedin two locations indicated in FIG. 4 .

TABLE 1 EDS location Element Weight % Atomic % Net Int. Error % K ratioSpot 1 C K 97.73 99.07 820.61 3.60 0.8682 O K 0.11 0.08 0.43 99.990.0003 P K 2.16 0.85 15.48 13.04 0.0175 Spot 2 C K 91.50 93.97 2293.332.85 0.8750 O K 7.35 5.67 76.64 12.37 0.0175 K K 1.15 0.36 17.83 19.520.0094

Example 2: Preparation of Phosphorus and Silicon Doped Carbon Nanosheetfrom Rice Grain

A total of 400 g of rice grain was washed thoroughly in 2000 mL ofdeionized water. The rice grain was filtrated and added to 1000 mL ofphosphoric acid, and stirred thoroughly. The mixture was exposed to 160°C. for 24 hours in a convection oven in air atmosphere to formintermediate mixture.

A sample size of 100 g of intermediate mixture was put in a quartzcombustion boat and placed inside quartz tube for heat treatment. Theintermediate sample was ramped at 10° C./min from 10° C. to 1000° C. andheld at 1000° C. for 1 hour. The thermal treatment was carried out in agas mixture containing 80 vol % argon and 20 vol % hydrogen gas, flowingat a total rate of 1000 L/min. The scanning electron micrographs of thefinal solid product are presented in FIGS. 5 and 6 . The elementalcompositions of the doped-carbon nanosheets is provided in Table 2 wherethe sampling was performed in two locations indicated in FIGS. 5 and 6 .In addition, as presented in Table 3, the gas adsorption shows thespecific surface area measurement data of the final product of 2625 m²/gand pore volume of 5.1 cc/g.

TABLE 2 EDS location Element Weight % Atomic % Net Int. Error % K ratioSpot 1, C K 88.76 92.20 1665.51 4.14 0.7232 FIG. 5 O K 8.64 6.74 81.5712.08 0.0211 SiK 0.35 0.16 11.86 20.66 0.0029 P K 2.25 0.91 56.84 7.320.0183 Spot 2, C K 88.81 92.29 1610.56 4.21 0.7178 FIG. 5 O K 8.43 6.5877.46 12.12 0.0206 SiK 0.36 0.16 11.61 20.63 0.0030 P K 2.40 0.97 59.227.05 0.0195 Spot 1, C K 88.76 92.20 1665.51 4.14 0.7232 FIG. 6 O K 8.646.74 81.57 12.08 0.0211 SiK 0.35 0.16 11.86 20.66 0.0029 P K 2.25 0.9156.84 7.32 0.0183 Spot 2, C K 88.81 92.29 1610.56 4.21 0.7178 FIG. 6 O K8.43 6.58 77.46 12.12 0.0206 SiK 0.36 0.16 11.61 20.63 0.0030 P K 2.400.97 59.22 7.05 0.0195

TABLE 3 Measured property Measured Value Surface Area (m²/g) Singlepoint surface area at P/Po = 0.200004002 2572.6885 BET Surface Area2625.1389 Langmuir Surface Area 6046.6273 t-Plot Micropore Area 162.4709t-Plot External Surface Area 2462.6680 BJH Adsorption cumulative surfacearea of pore 2831.605 between 17.000 Å and 3000.000 Å width Pore Volume(cm³/g) Single point adsorption total pore volume of 5.112336 pores lessthan 0.000 Å width at P/Po = 1.000675745 t-Plot micropore volume0.065579 BJH Adsorption cumulative volume of pores 5.291191 between17.000 Å and 3000.000 Å width Pore Size (Å) Adsorption average porewidth (4 V/A by BET) 77.8981 BJH Adsorption average pore width (4 V/A)74.745 DFT Pore Size Volume in Pores <18.09 Å (cm³/g) 0.48551 TotalVolume in Pores ≤387.34 Å (cm³/g) 3.58323 Area in Pores >387.34 Å (m²/g)0.000 Total Area in Pores ≥18.09 Å (m²/g) 1015.889 DFT Surface Energy(m²/g) Total Area 2573.750 Nanoparticle Size (Å) Average Particle Size22.856 Horvath-Kawazoe Maximum pore volume at P/Po = 0.9837220825.047021 (cm³/g) Median pore width (Å) 149.175

Example 3: Preparation of Multi-Element Doping of Carbon Nanosheet

A total of 300 g of cassava extract was placed in a 2000 mL Pyrex glassbeaker. About 50.0 g of potassium hydroxide was dissolved in a 1000 mLof deionized water and stirred thoroughly. Then, the cassava extract wasadded to the solution. This mixture sat for 6 hours and the soakedcassava extract was filtered out to remove excess solution. About 100 gof phosphorous acid was added to the filtered cassava extract andexposed to rapid and uniform heating for 10 minutes by using microwaveirradiation (1000 W). The intermediate sample was ramped at 15 C/minfrom 20° C. to 1000° C. and held at 1000° C. for 1 hour. The thermaltreatment was carried out in a gas mixture containing 90 vol % argon and10 vol % hydrogen gas, flowing at a total rate of 1000 L/min. Thescanning electron micrograph of the final solid product is presented inFIG. 7 , and the elemental compositions of the doped-carbon nanosheetsis provided in Table 4 where the sampling was performed in two locationsindicated in FIG. 7 .

TABLE 4 EDS location Element Weight % Atomic % Net Int. Error % K ratioSpot 1 C K 81.60 90.76 1049.06 6.15 0.5566 O K 4.33 3.61 34.95 32.060.0115 MgK 0.85 0.46 18.41 14.93 0.0066 AlK 0.55 0.27 11.46 21.84 0.0044SiK 0.86 0.41 17.32 15.54 0.0073 P K 5.31 2.29 77.12 6.83 0.0437 K 1.980.68 15.22 15.83 0.0163 CaK 4.53 1.51 26.11 14.38 0.0369 Spot 2 C K78.72 88.79 968.56 6.41 0.5201 O K 5.94 5.03 48.14 24.89 0.0161 MgK 0.880.49 18.95 14.13 0.0069 AlK 0.26 0.13 5.45 40.06 0.0021 SiK 1.00 0.4819.93 12.94 0.0085 P K 5.91 2.59 85.08 6.33 0.0488 K 2.37 0.82 18.0213.84 0.0196 CaK 4.91 1.66 28.04 13.20 0.0401

Example 4: Preparation of Multi-Element Doping of Carbon Nanosheet fromRice Grain

A total of 60 g of rice grain was added to 180 g of phosphoric acid, andstirred thoroughly. The mixture was exposed to 160° C. for 3 hours in aconvection oven in air atmosphere to form intermediate mixture. Theresulting product was soaked in 400 mL solution containing at least oneof; lithium acetate, sodium hydroxide, aluminium triacetate, calciumhydroxide, potassium hydroxide, magnesium acetate. This mixture sat for6 hours and the soaked product was filtered out to remove the excesssolution, followed by second heat treatment in inert atmosphere at 850°C. for 3 hours. The scanning electron micrograph of the final solidproduct is presented in FIG. 8 , and the elemental compositions of thedoped-carbon nanosheets is provided in Table 5 where the sampling wasperformed in two locations indicated in FIG. 8 .

TABLE 5 EDS location Element Weight % Atomic % Net Int. Error % K ratioSpot 1 C K 73.57 82.50 1393.70 6.38 0.4764 O K 15.17 12.77 217.26 13.250.0462 NaK 0.53 0.31 13.40 19.69 0.0035 MgK 0.60 0.33 19.86 15.26 0.0046P K 6.75 2.93 151.77 5.00 0.0555 K 2.37 0.81 27.66 11.52 0.0191 CaK 1.020.34 9.17 26.24 0.0084 Spot 2 C K 63.68 74.47 898.44 7.32 0.3660 O K21.93 19.26 285.64 10.36 0.0724 NaK 0.36 0.22 7.53 27.18 0.0024 MgK 0.780.45 21.69 12.87 0.0060 SiK 0.38 0.19 9.88 19.78 0.0032 P K 8.54 3.87161.84 4.94 0.0705 K 2.38 0.86 23.60 12.49 0.0194 CaK 1.94 0.68 14.6817.82 0.0160

Example 5

Doped carbon nanosheets with different morphologies were grown fromcassava extract, rice grain, or corn grain. Representative procedure isas follows: about 150 g of cassava extract was soaked in 500 mL solutioncontaining silicon oxide. This mixture sat for 6 hours and the soakedcassava extract was filtered out to remove excess solution. The soakedcassava extract was heated slowly from room temperature at a rate of 15°C./min to 1000° C. in a reducing atmosphere comprised of 10% hydrogengas flowing at 100 ml/min. The sample was held at 1000° C. for 1 hour inreducing atmosphere, then cooled down to room temperature under inertatmosphere. FIGS. 9, 10, and 11 show SEM images of wrapped-nanosheetsformed from pyrolysis of cassava extract, rice grain, and corn,respectively.

Example 6

About 20 g of corn grain was washed with 100 mL of potassium hydroxidesolution (5% concentration). The soaked corn grains filtered and washeated slowly from room temperature at a rate of 15° C./min to 800° C.in a reducing atmosphere comprised of 100% hydrogen gas flowing at 100ml/min. The sample was held at 800° C. for 1 hour in reducingatmosphere, then cooled down to room temperature under inert atmosphere.FIG. 12 shows an electron micrograph of the resulting wrapped graphenesheet-like structure mixed with bulk sheets substrate. Specifically,when corn was prepared at 800° C., the SEM image revealed afullerene-like morphology. When the temperature was increased to 900°C., the micrograph, FIG. 13 showed formation of small wrapped-graphenesheets grafted on larger wrapped-graphene sheets. When pyrolysis wascarried out at 1000° C., only wrapped-graphene sheets with a hurricaneshape was observed as shown in FIG. 14 . FIG. 15 shows a transmissionelectron micrograph of the resulting wrapped graphene sheet-likestructure.

Example 7

About 15 g of corn extract was heated slowly from room temperature at arate of 15° C./min to 1000° C. in a reducing atmosphere comprised of100% hydrogen gas flowing at 100 ml/min. The sample was held at 1000° C.for 1 hour in reducing atmosphere, then cooled down to room temperatureunder inert atmosphere. FIG. 16 shows an electron micrograph of theresulting wrapped graphene sheet-like structure with branches of smallernanosheets. The elemental composition of the nanosheets is provided inTable 6.

TABLE 6 EDS location Element Weight % Atomic % Net Int. Error % K ratioSpot 1 C K 91.50 93.97 2293.33 2.85 0.8750 O K 7.35 5.67 76.64 12.370.0175 K K 1.15 0.36 17.83 19.52 0.0094

Example 8: Fabrication of Lithium-ion Batteries

Lithium-ion batteries were fabricated with synthesized doped carbonnanosheet and the electrochemical performance of the resultingelectrodes was evaluated. The unusual combination of ultrahigh surfacearea and large pore volume of synthesized doped carbon nanosheetfacilitated Li-ion migration during charge and discharge cycles. Inaddition, the electrode reduce heat-build up and swelling that iscommonly experienced in graphite-based electrodes at high rates.

The coin cell (2032, Pred Materials) active anode material was made fromcarbon nanosheet prepared by according to procedure in Example 2.Several samples were tested with different adsorption properties: sampleA and sample B. Sample A carbon nanosheet had a BET surface area of 2343m²/g, pore volume of 4.9 ml/g, and the adsorption average pore width(4V/A by BET) of about 8.3 nm. Sample B had a BET surface area of 1879m²/g, pore volume of 3.9 ml/g, with an average pore width of 10.0 nm.

About 80 wt % synthesized doped carbon nanosheet powder, 10 wt %conductive carbon black (Timcal, Super C65), and 10 wt % polyvinylidenefluoride (PVDF) binder (Aremka, Kynar HSV900) were mixed with1-methyl-2-pyrrolidone (NMP) and the slurry was stirred overnight. Theslurry was cast onto a clean copper or aluminum foil current collectorand spread uniformly on the current collector using a doctor blade witha blade height of 20-500 μm. The electrode mass loading was 0.25-4.5mg/cm² active material. The obtained electrode sheet was dried overnightwithin a fume hood and then transferred to a 60° C. oven to bake theelectrode into a solid overnight. Discs (0.5 inches in diameter) of thedried electrode sheets were then pressed out and dried in a vacuum ovenat 120° C. for 16 hours.

The coin cell (2032, Pred Materials) was fabricated in an inertatmosphere glovebox (Argon, ≤1 ppm H₂O) using the electrode disc, aseparator (MTI Corp.), a metallic lithium counter/reference electrode,and Sigma-Aldrich electrolyte. The electrolyte consisted of 1 M LiPF₆ inethylene carbonate (EC): dimethyl carbonate (DEC). The volume ratio ofEC/DEC was 50/50. Galvanostatic charge/discharge measurements wereperformed over a voltage range of 0.01-3.0 V versus Li on an ArbinInstruments BT2043 test station using mass-normalized current of 37.2mA/g based on the active material mass.

FIG. 17 shows rate test of samples A and B, and FIGS. 18A-18C show therate test data of coin cell of sample B at different rates. This dataindicates that the trend of the rate data for both samples is similar,although their specific capacity are different at each test rate. Theinitial test data showed sample A has a specific capacity of 1900 mAh/gat a charge/discharge rate of 100 mA/g (0.1 C), which is a more than 5×increase in capacity of standard anode material, graphite, which has atheoretical capacity of 372 mAh/g. It was observed that at 0.1 C, 1 C, 2C, and 5 C test rates, the sample A exhibited specific capacity that wasalmost double of the sample B. Even at a test rate of 10 C, sample Aaverage specific capacity of 327 mAh/g was higher than that of sample B,191 mAh/g. Without being bound by a specific theory, it is believed thatthe increase in specific capacity of sample A is due to synergeticeffect of its higher surface area and pore volume compared with sampleB.

Doped-carbon nanosheet powders prepared by Example 2 were used toprepare composite slurries for fabricating 11 additional electrodes forLi-ion battery. The composition details of each slurry is as listed inTable 7. These slurries resulted in good adhesion and cohesion of thedoped-graphene on the current collectors.

TABLE 7 Components (wt %) Doped- Conductive Denka Ex. Graphene carbonblack CNT¹ Black NMC² CMC³ PVDF⁴ PEO⁵ SBR⁶ 8-1 90 10 8-2 90 5 5 8-3 84 13 12 8-4 91 1 2 6 8-5 90 5 5 8-6 90 10 8-7 90 5 5 8-8 45.5 45.5 1 2 68-9 91 0.5 0.5 2 6 8-10 50 50 10 8-11 10 50 10 ¹CNT is carbon nanotube;²NMC is lithium nickel manganese cobalt oxide; ³CMC is carboxymethylcellulose; ⁴PVDF is polyvinylidene fluoride; ⁵PEO is poly(ethyleneoxide); ⁶SBR is styrene butadiene rubber.

The electrochemical performance of cell that were fabricated using thecomposition 8-4 is presented in FIGS. 19 and 20 (as compared to baselineanode).

Example 9

The composited slurry of Example 8-4 prepared as disclosed herein wasused to fabricate a full cell comprising copper foil coated withoxygen/phosphorus doped-graphene (metal-free) as an anode, aluminiumfoil coated with metal-doped-graphene as a cathode, a separator (MTICorp.), an electrolyte, and a metallic lithium counter/referenceelectrode. The electrolyte comprised lithium hexafluorophosphate(LiPF₆). Tables 8 and 9 show the performance of the full cell.

TABLE 8 Coin Cell Results at 0.01 V/min Initial Capacity Cell g active D1 D 2 C 1 C2 (mAh/g) Baseline 0.005189 2.0613 1.9256 1.8807 1.8946397.24 1 0.00091 2.5589 0.4473 0.3673 0.3003 2811.9 2 0.001183 2.76810.4916 0.3859 0.3259 2339.8 3 0.000819 2.4329 0.4033 0.3451 0.27792970.5 4 0.001964 2.4167 0.4065 0.3386 0.2765 1230.4 5 0.000546 1.89640.344 0.3017 0.2391 3473.2 6 0.000728 2.3075 0.03964 0.343 0.2758 3169.6

TABLE 9 Full Cell Results Capacity Cell g active D 1 D 2 C 1 C2 (mAh/g)Doped-Graphene 1 0.00118 3.4311 0.5904 0.4488 0.3621 2900.33812 Anode 20.00127 3.0198 0.5026 0.4167 0.3269 2370.32967 NMC Cathode 2 0.014372.4662 2.1469 2.1403 2.1495 171.525942

It is understood that the examples and embodiments described herein arefor illustrative purposes only and that various modifications or changesin light thereof are suggested to persons skilled in the art and are tobe incorporated within the spirit and purview of this application andscope of the appended claims. All publications, patents, and patentapplications cited herein are hereby incorporated herein by referencefor all purposes.

What is claimed is:
 1. A process for preparing a carbon nanomaterial,wherein the carbon nanomaterial is doped and/or intercalated, theprocess comprising: providing a carbon-containing material to a reactorcomprising a solvent; providing one or more of: an oxidizing or reducingsolution, and a doping and/or intercalating agent to the reactorcomprising the carbon-containing material to obtain a reaction mixture,heating the reaction mixture to a temperature and for a time periodsufficient to obtain an intermediate material; contacting theintermediate material with one or more of hydrazine, lithium aluminiumhydride, diborane, and sodium borohydride; and then further heating theintermediate material to a temperature and for a time period sufficientto obtain the carbon nanomaterial.
 2. The process of claim 1, whereinthe carbon nanomaterial is Li-, Na-, O-, P-, K-, and/or Si-doped.
 3. Theprocess of claim 1, wherein the carbon nanomaterial is in a form of aparticulate, porous foam, film, or pellet, or is dispersed in a solvent.4. The process of claim 1, wherein the carbon-containing materialcomprises carbon nanosheet, graphene, fullerene, amorphous carbon,graphene oxide, carbon black, activated carbon, charcoal, carbonnanotubes, graphite, coal, or a combination of two or more thereof. 5.The process of claim 1, wherein said carbon-containing material is or isderived from the group consisting of cassava root, tapioca flour, yamroot, potato root, sugarcane, sugar beet, sucrose, rice grain, corn, andwheat grain.
 6. The process of claim 1, wherein the solvent is distilledwater, deionized water, ethanol, N-methyl-2-pyrrolidone, ethyleneglycol, propylene glycol, or a combination thereof.
 7. The process ofclaim 1, wherein the oxidizing or reducing solution is selected from oneor more of: sodium hydroxide, potassium hydroxide, hydrochloric acid,phosphoric acid, phosphorous acid, and nitric acid.
 8. The process ofclaim 1, wherein the doping and/or intercalating agent selected fromlithium chloride, 3,4-dihydroxybenzonitrile dilithium, lithiumhydroxide, lithium acetate, lithium citrate, lithiumbis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate,aluminium triacetate, calcium hydroxide, magnesium acetate, siliconoxide, and a combination of two or more thereof.
 9. The process of claim1, wherein the doping and/or intercalating agent is lithium acetate orsilicon oxide.
 10. The process of claim 1, wherein the temperaturesufficient to obtain the intermediate material is in a range of about 45to 1050° C., and the temperature sufficient to obtain the carbonnanomaterial is in a range of about 500 to 1500° C.
 11. The process ofclaim 1, further comprising washing the carbon nanomaterial withhydrogen peroxide or hydrochloric acid to obtain a washed carbonnanomaterial; rising the washed carbon nanomaterial with distilled ordeionized water to obtain a rinsed carbon nanomaterial; and heating therinsed carbon nanomaterial in an third gas at a temperature in a rangeof about 700 to 1500° C. to obtain the carbon nanomaterial having a BETsurface area of at least 1900 m²/g and pore volume of at least 2.4cm³/g.
 12. A process for preparing a carbon nanomaterial film, whereinthe carbon nanomaterial is doped and/or intercalated, the processcomprising: performing the process of claim 1 to provide a carbonnanomaterial; providing the carbon nanomaterial and one or more ofadditives selected from a conductive agent, binder, and thickeningagent, to a second solvent to obtain the slurry of the carbonnanomaterial; coating a surface of a substrate with the slurry to obtaina coated substrate; and heating the coated substrate to a temperatureand for a time period sufficient to obtain the carbon nanomaterial film.13. The process of claim 12, wherein coating is by tape casting, dipcoating, spray coating, spin coating, electronic printing, lamination,stamping, block printing, roller printing, screen printing, and heattransfer printing.
 14. The process of claim 12, wherein the temperaturesufficient to obtain the film is in a range of about 25 to 150° C. 15.The process of claim 12, wherein the film is configured for use in anelectrochemical cell.
 16. An electrochemical cell comprising: a cathodecomprising carbon nanomaterial film made by a method according to claim15, an anode, an electrolyte in fluid communication with the cathode andthe anode, and a separator disposed between the anode and the cathode.17. The electrochemical cell of claim 16, wherein the electrochemicalcell is configured as a coin cell, a pouch cell, a cylindrical cellform-factor, or a pack comprising two or more of the coin cells, pouchcells, or cylindrical cell form-factors.
 18. A process for preparing ananocomposite comprising a carbon nanomaterial, wherein the carbonnanomaterial is doped and/or intercalated, the process comprising:performing the process of claim 1 to provide a carbon nanomaterial; andproviding the carbon nanomaterial to a polymer to obtain thenanocomposite.
 19. The process of claim 18, wherein the carbonnanomaterial is provided in an amount sufficient to increase one or moreof mechanical, absorption, adsorption, electrical, electronic, magnetic,and optical properties of the nanocomposite by at least a factor greaterthan 1 compared to the same properties of the polymer.
 20. A process forpreparing a carbon nanomaterial, wherein the carbon nanomaterial isdoped and/or intercalated, the process comprising: providing acarbon-containing material to a reactor comprising a solvent; providingone or more of: an oxidizing or reducing solution, and a doping and/orintercalating agent to the reactor comprising the carbon-containingmaterial to obtain a reaction mixture, heating the reaction mixture to atemperature and for a time period sufficient to obtain an intermediatematerial; further heating the intermediate material to a temperature andfor a time period sufficient to obtain the carbon nanomaterial; washingthe carbon nanomaterial with hydrogen peroxide or hydrochloric acid toobtain a washed carbon nanomaterial; rising the washed carbonnanomaterial with distilled or deionized water to obtain a rinsed carbonnanomaterial; and heating the rinsed carbon nanomaterial in an third gasat a temperature in a range of about 700 to 1500° C. to obtain thecarbon nanomaterial having a BET surface area of at least 1900 m²/g andpore volume of at least 2.4 cm³/g.